Common Chemical Formula List

CHEMISTRY CLASS 9

CLASS WORK

Chemical formulae and equations

Derivation of formulae (key points)

Chemical Formula Definition: An expression which states the number and type of atoms

present in a molecule of a substance.

Chemical formulas such as HClO4 can be divided into empirical formula, molecular formula,

and structural formula. Chemical symbols of elements in the chemical formula represent the

elements present, and subscript numbers represent mole proportions of the proceeding

elements. Note that no subscript number means a subscript of 1.

From a chemical point of view, an element contained in the substance is a fundamental

question, and we represent the elemental composition by a chemical formula, such as H2O for

water. This formula implies that the water molecules consist of 2 hydrogen, and 1 oxygen

atoms. The formula H2O is also the molecular formula of water. For non-molecular substances

such as table salt, we represent the composition with an empirical formula. Sodium chloride is

represented by NaCl, meaning that sodium and chlorine ratio in sodium chloride is 1 to 1.

Again, the subscript 1 is omitted. Since table salt is an ionic compound, the formula implies that

numbers of Na+ ions, and Cl- ions are the same in the solid. The subscript numbers in an

empirical formula should have no common divisor.

Common Chemical Formula List

NaCl

Sodium chloride

H2O

Water

C6H12O6

Glucose

C2H6O

Alcohol

CaSO4

Sulfate Group

H2S

Hydrogen Sulfide

NaCl

Salt

O2

Oxygen

C2H6O

Ethanol

C2H4O2

Vinegar

NH3

Ammonia

MgCl2

Magnesium Chloride

C2H4O2

Acetic Acid

C4H10

Butane

NO3?

Nitrate

CuO

Copper Oxide

N2

Nitrogen

CO2

Carbon Dioxide

H2SO4

Sulfuric Acid

CH4

Methane

C12H22O11

Sucrose

C3H8

Propane

NaHCO3

Baking Soda

LiCl

Lithium chloride

F2

Fluoride

H2O2

Peroxide

C8H10N4O2

Caffeine

NaCl

Sodium Chloride

C9H8O4

Aspirin

HCl

Hydrochloric Acid

Zn(NO3)2

Zinc

CO

Carbon Monoxide

NaOH

Sodium Hydroxide

NaCN

Sodium Cyanide

Ca(CN)2

Calcium Cyanide

BALANCING CHEMICAL EQUATIONS

What is a balanced equation?

A chemical equation is balanced when the number of atoms of each type on each side of the

equation is the same. Which means if you have 12 hydrogens on the left hand side of the

equation, you must have 12 hydrogens on the right hand side, if there are 4 oxygens on the left,

there must 4 oxygens on the right, and so on. This is because of the law of conservation of mass

- you can't make or destroy atoms during a chemical reaction. But you can't just add atoms at

random to each side, you have to work with the molecules of the reactants. Also, you will find it

very tricky to try to balance a word equation, it is very much easier to use a chemical equation

with chemical symbols, as then you will be able to see how many atoms of each type are in

each chemical.

Example 1

Unbalanced Equation:- C3H8 + O2 ---> H2O + CO2

There are three carbons on the left, but only one on the right.

There are eight hydrogens on the left but only two on the right.

There are two oxygens on the left but three on the right.

Balanced Equation:- C3H8 + 5O2 ---> 4H2O + 3CO2

How do we balance the equation?

Balancing chemical equations isn't difficult, once you know the way to do it. Start by finding out

how many atoms of each type are on each side of the equation. Some teachers recommend

making a little table listing the numbers of each atom for the left hand side and for the right

hand side.

Next, look for an element which is in only one chemical on the left and in only one on the right

of the equation. (But it is usually a good idea to leave hydrogen and oxygen until you've done

the others first.)

To balance that element, multiply the chemical species on the side which doesn't have enough

atoms of that type by the number required to bring it up to the same as the other side. The

number is called the coefficient.

BUT

If you have to multiply by, say, 2 1/2, do so, THEN multiply EVERYTHING on each side of the

equation by two to get rid of the half.

We don't like having halves in equations, as you can't get half a molecule.

Now look for the next element or species that is not balanced and do the same thing.

Repeat until you are forced to balance the hydrogen and oxygens.

If there is a complex ion, sometimes called a polyatomic ion, on each side of the equation that

has remained intact, then that can often be balanced first, as it is acts as a single species. The

ions NO3- and CO32- are examples of a complex ion.

A VERY useful rule is to leave balancing oxygen and hydrogen to the last steps as these

elements are often in more than one chemical on each side , and it is not always easy to know

where to start. Some people also say you should leave any atom or species with a valancy of

one one until the end, and also generally leave anything present as an element to the end.

In Example 1 above, you would balance the carbons first, by putting a 3 in front of the CO2,

then balance the hydrogens by putting a 4 in front of H2O and finally the oxygens (which are in

more than one compound on the right, so we leave them until last) by putting a 5 in front of the

O2.

Example 2

Unbalanced equation:- H2SO4 + Fe ---> Fe2(SO4)3 + H2

Balance the SO4 first (as it is a complex ion and it is in one chemcial species on each side)

3H2SO4 + Fe ---> Fe2(SO4)3 + H2

Now balance the Fe (which is also in one chemical on each side)

3H2SO4 + 2Fe ---> Fe2(SO4)3 + H2

Finally, balance the hydrogen (although it is in one chemical species on each side, it is usually a

good idea to leave it until last)s

Balanced Equation:- 3H2SO4 + 2Fe ---> Fe2(SO4)3 + 3H2

We alter the coeficients in the equation.

Do NOT touch the subscripts for the atoms in a chemical species, or you will change it into an

different chemical. That would be a bit like saying I want six chicken legs for a meal, so I'll go get

a six-legged chicken. As chickens have two legs, you will need three normal, two-legged,

chickens, not a six-legged mutant monster, probably from outer space.

If you start by trying to balance something which is in more than one species on one side, you

can't easily tell which species you should have more of, and so can end up going round in

circles, continually altering things. If this happens, just start again, but balancing atoms or

complex ions that are in one species on each side. (This is important or it will not work.)

The City School

North nazimabad boys campus

Scheduled test

MCQ Chemistry

Class 9

Q.1. Choose the best answer:

I.

II.

III.

a. number of electrons

b. number of protons

c. atomic number

d. mass number

What is the general relationship between lattice energy and ionic bond strength?

a. The greater the lattice energy, the weaker the ionic bond

b. there is no relationship

c. the greater the lattice energy, the stronger the ionic bond

d. the weaker the lattice energy, the stronger the ionic bond

Magnesium oxide may be used for the lining of an electric furnace for making crockery. Which

properties of magnesium oxide help to explain this use?

A

B

C

D

IV.

/10

A strontium atom differs from a strontium ion in that the atom has a greater

strong forces

between

particles

Yes

Yes

No

No

ionic bonding

electrical

conductor

Yes

No

Yes

No

No

Yes

No

Yes

The table shows the electronic structures of four atoms.

atom

W

X

Y

Z

electronic structure

2,8,1

2,8,4

2,8,7

2,8,8

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